Based on the structural design of conventionally utilized adjustable-angle screwdrivers, most can only be firmly adjusted at two to three angles. Typically the usable adjustments are limited to perpendicular, straight or 45-degree angles. However, with regard to elaborate precision designed and exact assembled machine parts or mechanical devices, screwdrivers with these limited angles are completely unusable. Moreover, with regard to certain specific mechanical devices, if the product has few additional functions, or even no additional functions, then its relative added value is reduced and its relative natural market competitiveness is lowered. Unless there is low price cut-throat sales, adapting to market conflicts will be impossible.